Method for a Driver Assistance Application

ABSTRACT

A driver assistance system with improved fault tolerance and a method for the same are provided. For this purpose, a control variable for an actuator for a reduced driver assistance system is calculated in a second control unit.

Driver assistance systems such as active cruise control (ACC),overtaking assistant, lane departure warning systems, systems fortraffic sign recognition or lighting control, and autonomous brakesystems are components of modern vehicles.

In the systems that are currently approved, the driver is always part ofthe control loop, which means that the driver must remain attentive andintervene immediately if the driver assistance function fails. Suchfailure can be indicated, for example, by an alarm signal. In thefuture, it is planned to offer functionality for automated driving, i.e. the driver assistance system must be able to drive the vehicle safelyfor a predetermined period of time even in the event of a fault (such asa sensor failure). In this case, or if the driver does not immediatelyrespond to a takeover request, at least a reduced driver assistancefunction must be available until the driver takes over or the driverassistance system is fully functional again.

It is the object of this invention to provide a driver assistance systemwith improved fault tolerance.

This object is achieved according to the features of the independentclaims.

According to the invention, a method for a driver assistance system isprovided. The driver assistance system includes at least one sensor unit(S1, S2, . . . Sx) for detecting the surroundings, which may be designedas a radar, LIDAR and/or camera sensor. The driver assistance systemfurther comprises a first central control unit (SE1) with means forcalculating a surroundings model (5) at a high degree of precision. Thesurroundings model is based on the data from the at least one sensorunit, preferably a multitude of similar and/or different sensor units(S1, S2 . . . Sx) is provided that have the same or different ranges ofdetection. Furthermore, the first central control unit is configured tocalculate a control variable for a driver assistance application, suchas a lane-keeping system, and for transmitting a first control signal(3) for an actuator control system (6), e. g. for the steering system ofthe vehicle, in accordance with the calculated control variable. Asecond control unit (SE2) is provided and includes means for calculatinga second control variable based on data from the at least one sensorunit (S1, S2, . . . Sx) for a reduced driver assistance application (RF,RF1, RF2) and for transmitting a second control signal (4, 4 a, 4 b) tothe actuator control system (6). Furthermore, the driver assistancesystem includes an actuator with an actuator control unit. The secondcontrol unit is in particular a component of a sensor unit (S1, S2, . .. Sx) or an actuator control unit.

In the event that the first control signal (3) is not available, theactuator is triggered

-   -   using the second control signal (4, 4 a, 4 b), or    -   a third control signal for triggering the actuator is calculated        based on the last transmitted first control signal(s) (3) and        the second control signal (4, 4 b), or    -   the surroundings model calculated by the first control unit is        transmitted to the second control unit (SE2) and a second        control signal (4) for a reduced driver assistance application        is calculated based on said model. In particular, the        transmitted surroundings model can be updated with current data        from the at least one sensor unit (S1, S2, . . . Sx).

In a preferred embodiment of the invention, fewer control cases aretaken into account for calculating the second control variable (4, 4 a,4 b) for the reduced driver assistance application (RF, RF1, RF2) ascompared to calculating the control variable for use in the firstcontrol unit (SE1). In particular, control interventions are onlyperformed if, for example, a collision is inevitable or the vehicle isat risk to depart from the lane.

It is preferred that no interventions are performed for comfort requestsunder the reduced driver assistance application (RF, RF1, RF2). Comfortrequests include, for example, avoidance of abrupt transitions whencontrolling the longitudinal speed by limited acceleration or avoidanceof fast, multiple changes between two control states, e. g. a swingingsteering controller.

It is preferred that the calculation of a control variable for a reduceddriver assistance application (4, 4 a, 4 b) is performed in an actuatorcontrol unit at least twice, using either data from different sensorunits and/or different calculation methods (algorithms), and that acontrol signal for the actuator is calculated based on these at leasttwo second control variables.

In a positive embodiment of the invention, the at least one sensor unit(S1, S2, . . . Sx) includes means for preprocessing sensor data. Inparticular, preprocessing includes object or free space detection. Afterpreprocessing, the sensor data is transmitted to the first control unit(SE1) and completely or partially to the second control unit (SE2).

It is preferred that object or free space information is calculated in asensor unit according to a first method and a different second method(AL1, AL2, AL3, AL4) for preprocessing. The redundantly generatedinformation is checked for plausibility (7) for use in a surroundingsmodel in the first control unit, and only information based on one ofthe two methods (e. g. AL1 and not AL2) is used in a second control unit(SE2) for a reduced driver assistance application (RF, RF1, RF2). Inparticular, one of the methods (AL1, AL4) is optimized for the reduceddriver assistance application (RF, RF1, RF2).

In addition, a driver assistance system is claimed that includes atleast one sensor unit (S1, S2, . . . Sx) for detecting the surroundings,e. g. a radar, LIDAR, and/or camera sensor system, and a first controlunit (SE1) with means

-   -   for calculating a surroundings model (5) at a high degree of        precision based on the data from the at least one sensor unit        (S1, S2, . . . Sx) and    -   for calculating a control variable for a driver assistance        application, and    -   for transmitting a first control signal (3) in accordance with        the calculated control variable.

A second control unit (SE2) is provided and includes means forcalculating a second control variable based on data from the at leastone sensor unit (S1, S2, . . . Sx) for a reduced driver assistanceapplication (RF, RF1, RF2) and for transmitting a second control signal(4, 4 a, 4 b) to the actuator control system (6). Furthermore, thedriver assistance system includes an actuator with an actuator controlunit. The second control unit is in particular a component of a sensorunit (S1, S2, . . . Sx) or an actuator control unit. The driverassistance system further includes means for calculating andtransmitting a trigger signal for an actuator according to theindependent method claim.

The invention will be explained in more detail below with reference toexemplary embodiments and figures.

A preferred embodiment of the invention is shown in FIG. 1.Preprocessing is performed in the sensor units S1, S2, S3, Sx, forexample, an object and/or a free space is detected. A free space is anarea which the vehicle can currently drive into, e. g. a road sectionwithout obstacles. This data 1 is transmitted to a first control unit.The first control unit SE1 is the central control unit for driverassistance functions (ADAS-ECU) in this embodiment. The surroundingsmodel, a high-resolution image of the vehicle surroundings, iscalculated here using computing-intensive algorithms. The surroundingsmodel may, for example, be designed as an occupancy grid in which mergedobject data from surrounding objects is stored by various sensor units.The data 2 of the surroundings model is made available to the driverassistance application A1, A2, Ax, which derives a control variable 3for an actuator, e. g. for the brake, engine controller, and steeringsystem, from it. The actuator has its own controller, which typicallyhas a high ASIL level. Calculation of the surroundings model 5 and thedriver assistance application A1, A2, Ax A are optimized for highcomfort, for which also an increased use of resources with respect tocomputing time is accepted.

To provide a redundant path without a second powerful and expensivecontroller, the sensor data 1 is transmitted completely or partially tothe control unit of the actuator SE2. A reduced version of a driverassistance application is stored here, which derives a control variable4 from it. The reduced driver assistance application a minimal versionof the driver assistance application, which calculates the secondcontrol variable 4 using resources efficiently and without takingcomfort requirements into consideration.

So, if the first control unit SE1 fails, there is a second controlvariable 4 available that can be used to bridge the period of time untilthe driver takes over or until the full functionality of the firstcontrol unit is restored. The limited comfort of the reduced driverassistance application, e. g. a swinging steering controller, can serveas an additional warning to the driver alerting him or her to takecontrol of the vehicle.

In another embodiment, calculation of a multitude of reduced driverassistance applications is provided in the second control unit SE2. FIG.2 shows an example of this case based on two reduced driver assistanceapplications RF1 and RF2. These can be based on the data from a singlesensor or on data from various sensors or on merged data from multiplesensor units. The transmitted control variables 4 a and 4 b are checkedfor plausibility. If the control variables 4 a and 4 b cannot be checkedfor plausibility, each control variable 4 a, 4 b may for example beassigned a confidence value and the variable with the higher confidencevalue be selected for actuator control. The algorithms of the reduceddriver assistance applications RF1 and RF 2 may preferably be differentfrom one another and from the ones of the main application of the firstcontrol unit to be able to detect systematic errors in the analysis ofthe sensor data.

In a positive embodiment of the invention, the control variable 3 of thefirst control unit SE1 is further processed in the actuator for aplausibility check or fault strategy to bridge a limited period of timeafter a failure of the first control unit. In this way, another sourceof information is available for a limited period of time in combinationwith the control variable 4 or the control variables 4 a, 4 b of thereduced driver assistance applications RF1, RF2.

In a preferred embodiment of the invention, the surroundings model istransmitted to the second control unit and stored for a predeterminedtime. If the first control unit SE1 fails, the stored data can still beused for a specific period of time with a reduced driver assistancefunctionality. The data provided directly by the sensor units S1, S2,S3, Sx can supplement this history and thus facilitate a somewhat longerbridging time.

It is preferred to have the sensor units run multiple different methodsAL1 and AL2 or AL3 and AL4, e. g. for free space detection, to excludesystematic errors caused by algorithms. FIG. 2. shows a schematicdiagram of this process. The results of both methods can be checkedagainst each other for plausibility before they are merged. Furthermore,one of the sensor outputs can be particularly optimized for a reduceddriver assistance application RF1, RF2. In FIG. 2, these are the methodsAL 1 and AL 4. If AL2 and 3 are used in the first control unit SE1 forthe applications A1, A2, Ax, a completely different path to providingcontrol inputs can be realized via the reduced driver assistanceapplication RF. This path may be optimized for computing efficiencyrather than for comfort to save costs for the overall system.

1. A method for a driver assistance system, including i) at least onesensor unit for detecting the surroundings ii) a first control unit withmeans for calculating a surroundings model (5) at a high degree ofprecision based on data from the at least one sensor unit and forcalculating a control variable for a driver assistance application, andfor transmitting a first control signal for an actuator in accordancewith the calculated control variable, iii) an actuator with an actuatorcontrol unit iv) a second control unit (SE2) for calculating a secondcontrol variable for a reduced driver assistance application and asecond control signal for the actuator based on data from the at leastone sensor unit, wherein the second control unit is either disposed inthe sensor unit or in the actuator unit, wherein a third control signal(7) is determined for triggering the actuator in the event that thefirst control signal is not available, wherein the value of the secondcontrol signal (4) is used for the third control signal (7), or a thirdcontrol signal for triggering the actuator is calculated based on thelast transmitted first control signal(s) and the second control signal(7), or the surroundings model calculated by the first control unit istransmitted to the second control unit and a third control signal (7) iscalculated based on said model.
 2. The method according to claim 1,characterized in that less computing time is needed for calculating thesecond control variable for the reduced driver assistance application ascompared to calculating the control variable for the application in thefirst control unit because fewer control cases are considered.
 3. Themethod according to claim 2, characterized in that the reduced driverassistance application does not include any comfort requirements.
 4. Themethod according to claim 1, characterized in that the calculation of acontrol variable for a reduced driver assistance application isperformed in an actuator control unit at least twice, using either datafrom different sensor units and/or different calculation methods(algorithms), and that a control signal for the actuator is calculatedbased on these at least two second control variables.
 5. The methodaccording to claim 1, characterized in that the at least one sensor unitcomprises means for preprocessing sensor data, said preprocessingparticularly including object and free space detection, and that thesensor data is transmitted to the first sensor unit and the actuatorcontrol unit after preprocessing.
 6. The method according to claim 5,characterized in that for the preprocessing of a sensor unit, object orfree space information is calculated in accordance with a first methodand a different second method, then the redundantly generatedinformation is checked for plausibility for use in a first control unit,then further processed, and only information based on one of the twomethods is used in an actuator control unit.
 7. A driver assistancesystem for performing the method according to claim 1, including I) atleast one sensor unit for detecting the surroundings ii) a first controlunit with means for calculating a surroundings model (5) at a highdegree of precision based on data from the at least one sensor unit andfor calculating a control variable for a driver assistance application,and for transmitting a first control signal for an actuator inaccordance with the calculated control variable iii) an actuator with anactuator control unit iv) a second control unit (SE2) for calculating asecond control variable for a reduced driver assistance application anda second control signal for the actuator based on data from the at leastone sensor unit, wherein the second control unit is either disposed inthe sensor unit or in the actuator unit, v) means for calculating andtransmitting a trigger signal for an actuator in accordance with themethod.
 8. A method for operating a driver assistance system of avehicle including at least one sensor unit, a first control unit, anactuator control unit, an actuator, and a second control unitincorporated in the sensor unit, the actuator control unit or theactuator, wherein the method comprises: with the at least one sensorunit, detecting surroundings of the vehicle and producing correspondingsensor data; with the first control unit, attempting to calculate asurroundings model based on the sensor data, calculate a first controlvariable for a first driver assistance application, and transmit a firstcontrol signal to trigger the actuator dependent on and in accordancewith the first control variable; with the second control unit,calculating a second control variable for a second driver assistanceapplication having reduced functionality compared to the first driverassistance application, and transmitting a second control signal totrigger the actuator based on the sensor data; if the first controlsignal is not available, then determining a third control signal totrigger the actuator, wherein a value of the second control signal isused for the third control signal, or the third control signal iscalculated based on the second control signal and a last transmittedvalue of the first control signal, or the surroundings model istransmitted from the first control unit to the second control unit andthe third control signal is calculated based on the surroundings model.9. The method according to claim 8, wherein less computing time isneeded for calculating the second control variable for the second driverassistance application than for calculating the first control variablefor the first driver assistance application because fewer control casesare considered.
 10. The method according to claim 8, wherein the seconddriver assistance application does not include any driver comfortrequirements.
 11. The method according to claim 8, wherein the at leastone sensor unit includes at least two different sensor units that aredifferent from one another, wherein the second control unit isincorporated in the actuator control unit, wherein the calculating ofthe second control variable for the second driver assistance applicationis performed in the actuator control unit at least twice to produce atleast two second control variables respectively using the respectivesensor data from the at least two different sensor units and/or at leasttwo different calculation algorithms, and wherein the second controlsignal for triggering the actuator is calculated based on the at leasttwo second control variables.
 12. The method according to claim 8,wherein the at least one sensor unit includes a processor configured topreprocess the sensor data, wherein the method further comprisespreprocessing the sensor data including object and free space detectionof the sensor data in the processor of the at least one sensor unit, andwherein the sensor data is transmitted to the first control unit and tothe second control unit after the preprocessing thereof.
 13. The methodaccording to claim 12, wherein for the preprocessing, object or freespace information of the sensor data is calculated a first time inaccordance with a first calculation method to produce a firstpreprocessing result and calculated a second time in accordance with asecond calculation method different from the first calculation method toproduce a second preprocessing result, then the first and secondpreprocessing results are compared to one another to check forplausibility thereof and produce a plausibilized result which isprovided as the sensor data to the first control unit, and only eitherthe first preprocessing result or the second preprocessing result isprovided to the second control unit.
 14. A driver assistance system fora vehicle, comprising: an actuator configured and arranged to actuate acontrol component of the vehicle; an actuator control unit configuredand arranged to provide control signals for triggering the actuator; atleast one sensor unit configured and arranged to detect surroundings ofthe vehicle and produce corresponding sensor data; a first control unitconfigured and arranged to calculate a surroundings model based on thesensor data, to calculate a first control variable for a first driverassistance application, and to transmit a first control signal totrigger the actuator dependent on and in accordance with the firstcontrol variable; and a second control unit that is incorporated in thesensor unit, the actuator control unit or the actuator, and that isconfigured and arranged to calculate a second control variable for asecond driver assistance application having reduced functionalitycompared to the first driver assistance application, and to transmit asecond control signal to trigger the actuator based on the sensor data,and wherein the second control unit is further configured and arrangedto determine a third control signal to trigger the actuator if the firstcontrol signal is not available, wherein a value of the second controlsignal is used for the third control signal, or the third control signalis calculated based on a last transmitted value of the first controlsignal and the second control signal, or the surroundings model istransmitted from the first control unit to the second control unit andthe third control signal is calculated based on the surroundings model.